Davit mechanism device for launching lifeboats



Jan; 21, 1936.

T. H. MARTEN DAVIT MECHANISM DEVICE FOR LAUNCHING LIFEBOATS Filed Aug. 18, 195;

4 Sheets-Sheet l Jan. 21, 1936. T, A T N 2,028,513

DAVIT MECHANISM DEVICE FOR LAUNCHING LIFEBOATS Filed Au 18, 1951 4 Sheets-Sheet 2 Jan. 21, 1936. T. H. MARTEN DAVIT MECHANISM DEVICE FOR LAUNCHING LIFEBOATS Filed Aug. 18, 1931 4 Sheets-Sheet 5 lNVNTOR Thoma enr M ien mull H15 A NEY Jan. 21, 1936. T, MARTEN 2,028,513

DAVIT MECHANISM DEVICE FOR LAUNCHING LIFEBOATS Filed Aug. 18, 1931 4 Sheets-Sheet 4 INVENTOR Tho Henr Mg n HIS AT NEY Patented Jan. 21 1936 UNITED STATES PATENT OFFICE DAVIT MECHANISM DEVICE FOR LAUNCHING LIFEBOATS 28 Claims.

framing or other supporting means at. a ship deck level, and to the water, by a mechanism in which no part of the structure when in normal or stowed position of the boat cuts across or obstructs head room for persons; walking or standing on said ship deck, such as a promenade deck, including persons walking or standing close to the rail of such deck, immediately bencath the boat and davit.

Further objects are to provide a system or mechanism which accomplishes the above stated results, and in which the overall height of the davit structure above the ship deck level or equivalent is moderate, and usually no greater than required for ordinary head room and in which also no part of the structure when in normal or stowed position of the boat, is located below the! level of the said deck or outboard beyond the ships side.

A further object is to realize the previously stated objects or advantages in a structure no part of which, when in final launching position, is below the level of the outer edge of the said deck.

A further object is to provide a launching or hoisting cable or tackle arrangement which controls the sequential movements of the davit parts and the final launching movement of the boat in the launching operation, under influence of gravity, and which is also adapted to efiect the sequential hoisting operations including raising of the boat from the water and the movements of the davit parts to normal or boat stowing position, by use of a fall cable for each end of the boat.

Another object is to provide mechanism which will perform the launching operation under the force of gravity, with relative certainty under adverse conditions, as for example, if when the boat is on the starboard side of the ship, the

ship has a. substantial list to port.

A further object is to provide a structure the function of which is to effectively bring the vertical load of the davit proper and boat, when in the extended or outboard position, to rest solidly upon an extension of the fixed plate structure of the hull of the ship.

A further object is to provide a structure the function of which is to effectively produce fore and aft rigidity of the davit proper when in the extended or outboard position by absorbing these stresses by an extension directly or indirectly of the fixed plate structure of the hull of the ship.

A further object is to provide a combination of pulleys or sheaves and cable reeving the tunetion of which is to efiectively equalize the load on the cable and winch mechanism particularly in the hoisting or in-haul operations.

A further object is to provide an improved sheave, pulley or roller mechanism.

Another object is an improved water-way through the davit structure at its base.

Another object is an improved suspension hook at the davit head.

A still further and important object is to provide means for stationing the man in control of the launching movements of the davit and boat at a point, above the boat deck level where he has unrestricted view of all of the conditions with regard to both on the ship and down to the water, and to protect him from falling or being thrown away from his post.

Structures for realizing the stated objects, results and advantages, comprise, as briefly described, for each end of the boat, a fixed guide or track member located at an angle, but nearly horizontally, at a level only moderately above a normal persons head; another fixed guide or trackway in an approximately vertical position and extending upward a short distance from the ship deck level at its outward edge and not projecting beyond the ships side; and a movable davit structure having rollers or equivalent means for cooperation with the guides or tracks, such davit structure having an outward portion so arranged as to exert a powerful leverage efiect to produce or initiate launching movement of the boat by gravity. The davit structure aside Irom the tracks or guideways preferably consists of two main parts, one of which is in the nature of a lever arm spanning the gap between, and guided by, the trackways and having an outward portion which in stowed position provides the desired gravitational leverage force. Neither this lever arm member nor any other part of the davit structure when in stowed position encroaohes upon head room of persons standing or walking below on the ship deck, and when in intermediate and launching positions the lever arm member encroaches only slightly, if at all, upon such head room, including positions of persons at the rail of the ship deck; and no other part of the apparatus encroaches upon head room in any of its positions. The second or other principal part of the davit structure per se is the davit proper which is mounted to move longitudinally upon the lever arm member preferably after, but not necessarily after, the latter reaches its outward or launching position, wherein such member is in a generally outwardly and downwardly inclined position. Finally, the davit proper reaches a position in which its lowest part is substantially at and not below the edge of the ship deck and its upper end with the sheave thereon is located well outward for the final launching movement, i. e., lowering of the boat to the water.

All the stated movements are efiected in proper sequence by gravitational force under control of a fall cable running from a winch or equivalent control mechanism through the davit structure to the boat, and this cable also effects the necessary movements of the boat, lever arm member, and davit proper, in the hoisting and stowing operation.

Any suitable or standard winch mechanism may be used. Preferably, the winch mechanism consists substantially of a winding drum having its length divided into two parts, the cable from each such part serving, respectively, each of a pair of davits for one boat. I find it convenient and economical to so position two such winch mechanisms that each may in turn be served by a common motor and reduction gearing, a

clutch arrangement being employed to effect this common use of one power unit for two such mechanisms as and when required.

The characteristics and advantages of the invention are further sufiiciently explained in connection with the following detail description of the accompanying drawings, which show a representative embodiment. After considering this example, skilled persons will understand that many variations may be made without departing from the principles disclosed, and I contemplate the employment of any structures that are properly within the scope of the appended claims.

Fig. l is an elevation in a transverse plane of a ship with davit mechanism embodying the invention in one preferred form installed thereon, the showing being somewhat diagrammatic, with non-essential parts omitted for illustrative clearness, the boat being shown in normal or stowed position, and the davit mechanism in corresponding position.

Fig. 2 is a. similar view showing the parts in a position midway between the stowing and launching positions.

Fig. 3 shows the final launching position of the davit mechanism, with the boat hanging outboard, ready for final launching, i. e., lowering to the water.

Fig. 4 is a side elevation from outboard of Fig. 1, showing adjacent davits and boats and joint control bridge.

Fig. 4a is an elevation of essential parts of the winch mechanism.

Fig. 4b is a plan view showing the winch mechanism indicated in Fig. 4a, applied to a boat and its pair of davits and also to a second boat and its pair of davits, and the control bridge between and common to the two units.

Figs. 5 to 9 inclusive, are simplified diagrams explaining fundamental structural and operative features and principles of the invention.

Fig. 10 is an elevation of a preferred form of sheave or roller.

Fig. 11 is a vertical sectional view of Fig. 10.

Fig. 12 is an elevation from outboard of a part only of the davit structure in the position of Fig. 3.

Fig. 13 is a plan view of the parts in Fig. 12.

Fig. 14 is a plan view showing the parts in Fig. 13 at an intermediate stage.

Fig. 15 is a simplified diagram showing one scheme of reeving the cable.

The structural and operative principles of the davit mechanism, aside from the winch mechanism, are readily understood from diagrammatic Figures 5 to 9. In Fig. 5, D represents a fixed guide or trackway which may be in a horizontal or nearly horizontal position, but which is preferably inclined as shown, above a level corresponding to the head level of a normally tall person. F is a fixed guide or trackway in approximately vertical position at the ships side but preferably not projecting outwardly therefrom; its lower end is at the level of the boat deck and it need extend upwardly only a moderate distance, and preferably slopes slightly inboard, as to a point slightly above the hand rail of that deck. The davit element is represented in Fig. 5 by the generally curved line K, as being in one piece, with a curved upper portion to overhang one end of the boat which is suspended from the end N of the upper curved portion. The lower end E of the outward or lower curved portion of the davit element engages and moves on the fixed vertical guide F, while a main pivotal or fulcrum point A adjacent the lower end of the upper curved portion in effect engages and moves on the fixed inclined guide D.

The portions of the complete davit element K extending outward from the main pivot point A are of substantial reach and mass, providing a gravitational leverage force, or, as otherwise described, the center of gravity of the davit structure, with or without a boat suspended therefrom, is outboard in relation to the main pivot or fulcrum point A so that when the fall cable (not shown in the diagrams) is slacked away the complete davit element K moves outwardly, the toe E being gravitationally pulled downward on the fixed vertical guide F drawing the pivot point A outward and upward along or on the fixed inclined guide D.

At the commencement of an outward or launching movement there is a powerful gravitational leverage movement exerted by the outwardly extending portion of the davit element K, insuring the commencement of the launching movement by force of gravity under normal or favorable conditions, as when the ship is on an even keel, and also under unfavorable conditions, as when the ship has an adverse list, for example, if the davit, as viewed in Fig. 5, is on the starboard side and the ship has a substantial list to port, the gravitational leverage effect of the outward portion of the davit element K will nevertheless produce an outward movement of the inward portion of the davit element K, insuring the initiation and continuation of the launching action by gravity. As soon as launching movement commences the weight of the upper part of the structure and of the boat, if the boat is carried by the davit, are thrown progressively farther outward in relation to the ship and to the main pivot point or gravitational support A, thus progressively moving outwardly the location of the center of gravity of the entire moving system, so that as the lever arm part of the davit element increases the angularity of its position, and progressively loses leverage effect, it will have assumed an angle sufficient in itself to insure the completion of the launching movement.

At the end of the stated movement, davit element K is in the position of Fig. 6 with the toe E at the bottom of its guide and the boat suspended from the upper end practically above the ship's side.

To provide for further outboard movement of the boat, Fig. 7 shows that the complete davit element K is preferably made in two main parts K and K of which the general or outward part K is correctly described as a lever arm having also a supporting and guiding function for the upper part K which is correctly referred to as the davit proper, the lower part or base of K being movably guided longitudinally on the part K It is now evident that the position of Fig. '7 is an intermediate position of the launching movement, as also represented in Fig. 6.

Further paying out of the fall cable now permits the davit proper, K with or without the boat, to move down and outward upon the part K through a subsequent intermediate position,

r the lower end of the lever arm K so that when a boat is carried, it is hung out from the 'ships side even under adverse conditions of list, as above referred to. The boat is then lowered to the water. It will be noted that in the movementof the davit proper K from the position of Fig. 5 to that of Fig. 9, the center of gravity of the davit proper is well outward in relation to other parts and positive movement under the force of gravity is insured.

The leverage effect of the lever arm K commencing at its normal or stowed position, is sufficient also to overcome adverse conditions including a moderately defective condition of the mechanism due to inadequate inspection or maintenance, such as sticking of the fall cable, rust in the sheaves, etc., or insuificient freedom throughout the davit or winch mechanism due to any cause.

In the hoisting operation the parts operate to move in reverse sequence. Thus, when in the position of Fig. 9, when the fall cable is overhauled by the winch, the boat is first raised to the upper end N of the davit proper, the davit proper K is then traversed upward and inward on the lever arm K to an eifective stop acting between the parts K and K see Fig. 7, and then the davit proper K with the lever arm K moves substantially inward with the pivot center A moving inward and downward along the fixed inclined guide D to the inward limit, and the toe E of the lever arm K rising on the fixed vertical guide F. The parts are then again in the position of Fig. 5.

These structural and operative principles: are

shown in Figs. 1 to 4 embodied in one form of practical apparatus. The showing in these figures is also somewhat diagrammatic in the respect that non-essential details are omitted for the sake of illustrative clearness. These figures show oneend of a boat ID in stowed position slightly above a level II which represents a desired boat level, for purposes of using the boat deck for a clear promenade deck.

As shown in Fig. 1, the boat is located in stowed position slightly above the horizontal portions l2 of a frame or beam structure I 3, the purpose of which is solely to support the upper fixed inclined trackway and the lower fixed vertical trackway, and is curved as shown for appearance only, and to just clear the keel of the boat in movement, the curve extending approximately vertically downward for the said purpose to a point [4 which is practically at the lower end of the lower fixed vertical trackway F and at the level of the boat deck 15.

One suitable winch mechanism, as previously referred to, is shown in Figs. 4a and 4b, which may be located upon the upper deck level l8 inboard of the davits and boat and at a location for convenient control from the control bridge IT, as hereinafter set forth.

An additional and important feature of the complete invention is the control bridge H, which preferably located between each pair of boats, as indicated in Figs; and 4b. This feature of my complete invention provides means for one operator to take charge of the launching operations of a pair of boats, though I do not'restrict myself to the number of control bridges with respect to any given number of boats to be handled. Fig. 4b is a plan view of the control bridge which may in effect be an extension of the upper, or sun, deck l8, carried outwardly to a point close to the line of the ships side I9, between the boats as shown and provided with a railing 20, preferably breast high, around three sides to protect the operator. The brake control lever 2| and the motor control 22 are located on the bridge as more particularly shown in Figs. 3, 4 and 4b. Thus, an operator can clearly observe all of the conditions affecting the boat he is operating as regards conditions both on deck and overside, in the complete launching operation and recovery, i. e., from stowed position to the water and reverse.

The outward or, lower fixed vertical guide or trackway F, also previously referred to, is located on or may be a part of the lower approximately vertical portion of the beam 13. This lower fixed vertical guide F is preferably of double channel section, with the channels back to back so that the flanges are directed outward (toward the eye as viewed in Fig. 1, etc.). The lever arm K is preferably also of double channel section but with the channels face to face so that the flanges are directed inward. At its lower end the lever arm K has a guide roll 23, whose axis is at the point E of the diagrams Figs. 5 to 9, rolling in the boxed guide of the.

fixed vertical trackway F, the roll 23 rolling on the plate 24, fixed to the inward flanges of the vertical portions of the beams l3. At its upper or inward end the lever arm K has a guide roll 25, rolling on the fixed inclined trackway D, which, as illustrated, has an inward stop formation 26, (Figs. 2 and 3) and an outward stop! formation 21, (Fig. 1,) to limit movement of the lever arm K by cooperation with its roll 25.

The davit proper K has, at opposite ends of its base, guide rolls 28 and 29, respectively, rolling in the guideway provided by the double! channel formation of lever arm K At the end of the overhanging or upper portion 30 of the davit proper is a cable pulley or sheave 3|, at an axis which corresponds to the point N of the.

diagrams, Figs. 5 to 9, and the boat is suspended from the fall cable C, below the sheave 3| by means of the sheave 32 on the boat which latter sheave permits the return of the cable to the davit proper where its end C see Figs. 4 and 15, is made fast in any suitable manner. The davit proper has also other suitable guide sheaves for the cable C arranged to properly carry out that feature of my complete invention which provides for an equalizing of cable tension and winch load throughout the various operations of the system as described, thus, see Fig. 15, tracing the cable C from its end C above referred to as made fast to the davit proper at the boat suspension point N, it passes down and around the sheave 32 on the boat and back to sheave 3|, thence over guide sheave 33 to sheave 34; from sheave 3 the fall cable C passes around sheave 85, mounted on the lever arm K preferably, slightly above the axis of the guide roll 25 and passes back again and around a second sheave 36, mounted beside sheave 3t, and returns to and passes over a guide sheave 31, mounted on the axis of the roll 25, and from this point the cable C goes over guide sheave 33 fixed to the ship structure and thence to the winch as later described.

An important feature of the complete invention is the improved type of long billed hook 39, located below the upper and outer overhanging end of the davit proper. Hooks of this general type have been previously used, but have been in a fixed position in relation to the davit, the

unhooking operation being dependent upon the overturning action of the davit. My improved hook is pivotally mounted adjacent the axis of the sheave 3| and is afforded a sufficient latitude of swing, so that the pin 40 mounted on, and forming a part of, the boat sheave 32, is held positively engaged by the hook until the davit proper has reached a point close to its final outboard position. A light cable 4| is connected at one end to the long lever shank 42 of the structure of the hook 39 and is connected at its other end to a fastening iZa on the lever arm K after being led over suitable guide sheaves carried by the davit proper Kl] Throughout the major portion of the forward movement of the davit proper K in the guideway of lever arm K the cable ii retains sufficient slack to permit the hook 33 to swing outwardly with the pin it until the davit proper K approaches closely to full outboard position at which point all slack in the cable 4%! is taken up so that the further and remaining movement of the davit proper K to full outboard position causes cable Al to pull hook 39 quickly out of engagement with pin lil thus efiectively disengaging the boat sheave 32 from the davit proper K I do not restrict myself to any given point on the davit structure to which the operating end of the cable t! is to be made fast, nor do I restrict myself to a flexible line, that is to sayz-the operating means may be a rod or a series of rods linked together to effect disengagement of the hook and boat sheave. This feature of my invention is to maintain complete engagement of the hook 39 with the pin 6%, until it is desired to quickly effect complete disengagement at a speed disproportionally rapid as compared with the speed of the overturning movement of the davit proper.

The operation of launching the boat is substantially the same as described in connection with the diagrams. The operator assumes his position on the control bridge ll, where he has contact the same.

under his hand the lever 2!, controlling the brake means 42, see Figs. 4a and 4b, connected with the winch, by which means he is able to slack the fall cable C. When the fall cable is slacked off at the winch, its restraining pull exerted at the point 25 of the movable system is relaxed. The lever arm K and especially the outward and lower portion thereof, is so arranged that it exerts a powerful gravitational leverage effect on the entire movable system. This lever arm K with or Without the davit proper K and with the boat hanging in the upper hook 39, immediately and under normal or adverse conditions, as sufficiently referred to above, commences to move generally outward and downward, the extended end on the guide roll 23 gravitationally pulling and moving down in the guide F of the fixed vertical trackway and the guide roll 25 being thus hauled along and upwardly on guide D of the fixed inclined trackway, until checked by engagement with stop 21,

and guide roll 23, corresponding also to point E of lever arm K is then at the bottom of its guide F. The parts are then in the intermediate position of Fig. 2 which also corresponds to diagrammatic Figures 6 and 7. The operator continues to further permit the cable to be drawn from the winch, thus effecting gravitational descent of the davit proper K, with the boat hanging in engagement with the hook 39, the guide rolls 28 and 29 rolling down in the guide formation of lever arm K until in the final launching position of the davit mechanism, see Figs. 3 and 9, the cable line li, having, at its predetermined time, been drawn taut, disengaging the hook 39. As appears in Fig. 3, roll 29 is approximately at the bottom of the guide formation of lever arm K and also near the bottom of guide F, but it must be clearly understood that the davit proper K does not rest upon this roll 29, nor upon this part of its structure. As the davit proper K reaches the position shown in Fig. 3, the brackets 43 carried by the davit proper K come to rest on the saddles. 44, which preferably form a part of the fore and aft bracing plates 45 of the fixed vertical guide F. Thus the vertical load of the davit proper K and of the boat and boat load rest upon this fixed upward extension 45 of the plating GS of the hull structure of the ship, the lever arm K being thus relieved of those stresses. The brackets 43 and saddles dd form the stop for the davit proper K in this position, and which form in effect a fulcrum around which the overturning tendency only of the load is controlled by the rolls 28 and 29 of the davit proper K and the lever arm K As the davit proper approaches the position shown in Fig. 3, the wedge pieces M, see Fig. 14, etc., carried by the davit proper K" enter the space formed between the saddles 44 and solidly In this manner fore and aft stresses set up by a fore and aft swinging of the boat, or from any other causes, are communicated to this fixed upward extension d5 of the hull structure 36 of the ship, the lever arm K being thus relieved of those stresses. In general terms the davit proper K in the position shown in Fig. 3, becomes integral in structure with the solid hull structure of the ship, see Figs. 12 and 13.

As shown in Fig. 3, the upper portion 39 of the davit proper K and its sheave 3! are located well outboard, so that the boat is swung out from the ships side and thereafter is lowered to the ll, himself protected by the railing 20.

water, all under the unobstructed observation and control of the operator on the control bridge It should be understood of course that the loading of passengers into the boat may be effected at the normal or stowed position or at any point in the launching operation according to the direction of the officer in charge. The operator can hold the system stationary at any point in its movement by operation of the brake control hand lever 2 I.

To raise the boat from the water and return the davit system to normal or stowed position, the fall cable C is overhauled by the winch G8, and the parts move in reverse order. It will be noted that with the reeving of the fall cable C as described, that the boat is hauled up to the davit proper by a two-part purchase, whereas when the combined boat and davit proper are hauled up the lever arm K the three-part purchase between the sheave centers 34 and 35 is effective until this span is closed up and then the single-part purchase of the remaining inhauling operation, effects the return of the entire system back to stowed position, thus effectively equalizing the pull on the cable and consequently likewise the load on the winch and power source, etc. v

It should be noted here that for purposes of proper, functioning in the launching or forward movement the three-part-purchase between sheave centers 34 and 35 tends to maintain the normal relation, with some flexible variation, between the lever arm K and davit proper K. Thus the lever arm K may not always reach its full forward position before any movement of the davit proper K thereon takes place. Under different conditions sequence of movement may vary within minor limits. The system is designed to seek, as a whole, and in its parts, a condition of gravitational equilibrium with proper allowance for rolling or listing of the ship and for uncertain frictional resistance.

It will now be understood by reference to Fig. 1 that in stowed position no part of the davit structure encroaches upon head room of persons standing or walking on the boat deck, such as promenade deck I5, including persons standing or moving at the rail 49, and when in intermediate or launching positions no part of the mechanism, except a small part of the lever arm K encroaches upon such space or head room and that only slightly at a point near the curve of the beam I3. No part of the davit structure in launching position is located below the level of the boat deck I5 and no part of the supporting or guiding means, such as guide-F, is located outward of the ships side or below the level of the said boat deck.

There is no davit guide member extending upward at a sharp angle interfering with head room above the boat deck level, since the present system with its gravitational leverage action provides a proper initial forwardly and outwardly launching impulse under gravitational force, without the necessity for any initial sharp downward path or guide arrangement or generally high location of the davit mechanism and boat above a desirable normal level.

A winch mechanism which may be used with the present invention, indicatedby the lead of the cable, in Figs. 1 to 3, may be located inboard on the upper deck level I8, shown in top plan in Fig. 4b and in a corresponding side elevation in Fig. 4a, in semi-diagrammatic form for illustrative clearness. It consists essentially, for one boat, of a double winding drum 48 and 50, so arranged with a suflicient length of cable lead to insure proper winding. The cable C is led from drum 50 to the sheave 59, thence outwardly to the far davit and thence to the boat. The cable intended for the near davit is first led out to sheave 60, to provide a sufiicient length of lead to insure even winding and is then' led back to sheave GI and thence to the near davit and to the boat.

Any suitable power and transmission means may be used, such as the motor 51, gear reduction 52, clutch 53, transmission shaft 54, driving bevel pinion 55, and driven bevel gear 56, the latter being integral with the double drum.

The drum is carried by bearings 51 and 58 at either end, the bearings being mounted upon suitable support brackets bolted to the deck I8.

Such winch mechanism may be advantageously used in many locations in relation to the ship structure, davits, and boats.

As appears in Figs. 4, 12, 13 and 14, the fore and aft stifiening plates 45 are each preferably solidly riveted to the uppermost plate 46 of the hull structure and extend to a substantial distance fore and aft of the guide F. These plates 45 are riveted upwardly to the vertical channel members of the fixed beams I3, which latter form the guide F, with their outer edges cut to form a gore as shown, thus forming solid foreand-aft braces for the guide F, and solid compression supports for the vertical weight taken by the saddles 44 at their upper ends when the fore-and-aft brackets 43 carried by the davit forms an important part of the invention. In

a davit structure of the class described it is desirable to avoid if possible the use of oil and grease and at the same time to guard against an accumulation of rust and the like obstructing freedom of operation.

To secure extreme freedom in all bearings I provide a sheave or roller comprising a fixed hub member of large diameter and broad surface around which the ring 66 rotates on rollers 61, arranged between the two members as shown, the whole arranged between side retaining disks or plates 68 as shown. ,In the case of sheaves, or pulleys, the ring 66 is grooved to take the cable, etc., whereas in the case of rolls, or wheels, the ring is not grooved. This feature of my combined invention resides in arranging the small rollers 61 far out on the radius of rotation, close to the cable in the case of sheaves, etc., and close to the outer traction surface in the case of rolls, or wheels, so that the rollers 61 may be loose and free without unduly in creasing this freedom on the cable or traction radius. I find as a result of tests that if the rolling surface is substantially wide, and speed is not excessive, that steadiness of operation results although extreme clearance is provided for the rollers 61 and when no oil or grease is used. Absence of oil or grease is important in respect of any gear on shipboard underneath which passengers are required to stand or move about. Suitable metal may be introduced to avoid rust, etc. In Figs. 1, 2 and 3, my improved waterway is shown by the opening 69 through the base of the vertical guide F at its lower extremity where the structure forming the guide F is fastened to the ships plating at the outer edge of the deck i5. Thus the water is allowed free passage through the structure. In this connection I also provide the oblong opening '56, see Figs. 4 and 12, serving as a scupper, facing outboard.

The various novel features of my combined invention, particularly with respect to its operative efiiciency in combination with its economic advantages in saving unobstructed, for passenger use, valuable deck space, will be readily appreciated by those skilled in the art.

Whereas, I have described my invention by reference to specific forms thereof, it will be understood that many changes and modifications may be made without departing from the spirit of the invention.

I claim:

1. A davit structure comprising a movable supporting and guiding track member, track means normally supporting said movable sup porting and guiding track member above a ship deck with its outward end adjacent the ship side and also guiding said movable supporting and guiding track member to move outward and downward with its outward end to a lowered position at the ships side, a davit proper having an arm formation for boat suspension and movably mounted on said movable supporting and guiding track member for normal location inboard above the deck and for movement outward with and downwardly upon said member to a lowermost position in which the davit arm projects outboard from the ship side, positioning the boat for lowering, and common means for limiting the respective extents of downward and upward movements of said movable supporting and guiding track member upon said supporting track means.

2. The structure defined in claim 1 with the addition of a winch and a fall rope operated by the winch and connected through the davit to the boat and controlling the outward movements by gravity of the guiding member and davit successively and thereafter the lowering of the boat.

3. The structure defined in claim 1 with the addition of a winch and a fall rope operated by the winch and connected through the davit to the boat and controlling the outward movements by gravity of the guiding member and davit successively and thereafter the lowering of the boat, and also by reverse movement effecting hoisting of the boat and inward movements of the davit and guiding member successively.

4. The structure defined in claim 1 with the addition of winch mechanism, and a fall rope operated by the winch mechanism and connected through the davit to the boat.

5. The structure defined in claim 1 with the addition of winch mechanism, and a fall cable operated by the winch mechanism and connected through the davit to the boat, the winch mechanism comprising a double drum whereby two cables are led to the davits and'boat for operation in unison.

6. A davit structure comprising a supporting and guiding member of generally curved form in a vertical plane, a trackway normally supporting the inward end of the member above a ship deck with its outward end adjacent the ship side and a trackwa-y guiding the outward end of the member to move downward to bring its outward end in a lower position at the ships side, and a davit proper having an arm formation for boat suspension and movably mounted on the guiding member for normal location inboard above the deck and for movement with and downwardly upon said member to a lowermost position in which the davit arm projects outward from the ships side, positioning the boat for lowering.

7. The structure defined in claim 1, with the addition that said davit structure is in duplicate for one boat, the collective structure comprising winch mechanism, and a fall rope operated by the winch mechanism and connected through the davit structure to the boat, and driving and controlling mechanism including a motor and arranged to operate both davit structures in unison.

8. In combination with a ship having a boat deck, a guide-way inclined upwardly and outwardly substantially above the deck level, another guide-way adjacent the ship side extending substantially vertically upward from the deck level, a supporting and guiding member of generally curved form in the vertical plane, means guiding the inward end of the member for inward and outward movement on the inclined guide-way and upward and downward movement of the outward end on the vertical guide-way and a davit proper mounted for inboard and outboard movement with and relative to the guiding memher.

9. The structure defined in claim 8 with the addition of winch mechanism mounted substantially below the davit, and a fall rope operated by the winch mechanism and rove through pulleys in the davit including a pulley at the end of the davit proper by which the boat is suspended.

10. The structure defined in claim 8 with the addition of winch mechanism mounted substantially at the level of the davit and a fall cable operated by the winch mechanism and rove through pulleys in the davit including a pulley at the end of the davit proper by which the boat is suspended, the winch mechanism comprising a drum, a brake for controlling the speed of the drum for unwinding the cable and a motor for operating the drum to rewind the cable.

11. A davit mechanism comprising an upper, rearwardly and downwardly inclined guideway, a lower, approximately vertical guideway, and a davit structure comprising a lower arm portion and an upper overhanging boat supporting portion, the davit structure having a fulcrum point movable on said upper guideway and a lower controlling point movable on said lower guideway.

12. A davit mechanism comprising an upper, rearwardly and downwardly inclined guideway, a lower, approximately vertical guideway, and a davit structure comprising a lower arm portion and an upper overhanging boat supporting portion slidably associated therewith, the davit structure having a fulcrum point movable on said upper guideway and a lower controlling point movable on said lower guideway, the arm portion outward from the fulcrum being of a form and mass having a leverage action to' produce outward movement of the davit structure by gravity alone.

13. A davit mechanism comprising an upper, inclined guideway, a lower, approximately vertical guideway, and a davit structure comprising a lower arm portion and an upper overhanging boat supporting portion, davit structure having a fulcrum point movable on said upper guideway and a lower controlling'point movable on said lower guideway, the arm portion outward from the fulcrum being of a form and mass having a gravitational leverage action, the upper overhanging portion of the davit structure being independently movabie by gravity on the lower arm portion.

14. A boat davit, a trackway, means for supporting said davit to be movable by gravity on said trackway, a second trackway, means for mounting said second trackway on a ship to extend over the ships side, and means for mounting said first-named trackway to be movable by gravity on and substantially within the limits of said second-named trackway.

15. In a device for launching a boat from the deck of a ship comprising a davit arm from which the boat is suspended, a guidewayfastened to the outer edge of the deck and extending upwardly and inwardly within which the davit arm moves, the combination with the lower portion of the guideway of fore-and-aft stifiening plates fastened near their lower edges near the deck level to the plating of the hull of the ship and fastened at their respective inner edges to the upwardly extending portion oi. the guideway and with their respective fore-and-aft edges gored to taper upwardly and toward the guideway and a space extending upwardly from the edge of the deck between the two said inner edges to permit passage of the davit arm.

16. In a device for launching a boat from the deck of a ship comprising a davit arm from which the boat'is suspended, a guideway fastened to the outer edge or the deck and extending upwardly and inwardly within which the davit arm moves, the combination with the lower portion of the guideway of fore-and-aft stress plates connecting the foot of the upwardly extending portion of the guideway to the plating of the ship near the edge of the deck and a space extending upwardly from near the level of the deck between the said fore-and-aft plates to permit passage of the davit arm.

1'7; The structure defined in claim 15 with the addition of saddles forming the upper part of the fore-and-ait stiffening plates and fore-andait brackets carried by the davit arm and adapted to seat themselvse in and upon the said saddles.

18. In a device for launching a boat from the deck of a ship comprising a davit arm from which the boat is suspended, a guideway fastened to the outer edge of the deck and extending upwardly and inwardly within which the davit arm moves, fore-and-aft stress plates fastened near their lower edges near the deck level to the plating of the hull of the ship, and fastened at their respective inner edges to the upwardly extending portion of the guideway and with their respective fore-and-aft edges gored to taper upwardly and toward the guideway, and a space extending upwardly from the edge of the deck between the two said inner edges to permit pas sage of the davit arm, saddles forming the upper part of the fore-and-aft stress plates, fore-andaft brackets carried by the davit arm and adapted to seat themselves in the saddles, wedge pieces carried by thedavit and adapted to guide the approach, and centralize the seating, of the brackets in andupon the saddles as the davit arm reaches its outermost position, to lock the brackets and saddles together in the fore-andait direction to transmit the fore-and-aft stresses of the davit arm to the said stress plates and thence to the plating of the hull of the ship.

19. The structure defined in claim 15 with the addition of fore-and-aft' brackets carried by, and

forming part of the davit arm, saddles carried by, and forming part of the fore-and-aft stiffening or stress plates, means for seating the brackets in and upon the saddles as the davit arm reaches its outermost position to transmit the vertical and fore-and-aft stresses of the davit arm to the saddles and thence to the said stress plates and to the plating of the hull of the ship by direct through contact effecting thereby a combined stable and rigid structure.

20. The structure defined in claim 15 with the addition and a fore-and-aft opening through the foot of the guideway forming a waterway in alignment with the regular ship's waterway at the edge of the deck.

21. In a device for launching a boat from a shipcomprising a davit arm from which the boat is suspended and a movable trackway upon which the davit arm moves, the combination of' tween the davit arm and the trackway relative to the purchase between the davit arm and the boat upon movement of said davit arm relative to said trackway.

22. The structure as defined in claim 21 in that cable sheaves are disposed on the boat, cable sheaves are disposed on the davit arm, cable sheaves are disposed on the lever arm, cable sheaves are disposed on the ship, and a winch disposed on the ship, whereby the cable threaded through the system effects its least purchase between the ship and the lever arm, its greatest purchase'between the lever arm and the davit arm, and its intermediate purchase between the davit arm and the boat, and thereby eflects equalization of cable tension and winch load.

23. A ship's davit comprising a fixed trackway, a second trackway mounted on said fixed trackway and movable under gravity thereon and a davit mounted on said second-named trackway and movable under gravity thereon.

24. A ships davit comprising aatrackway, a second trackway mounted on said first-named trackway and movable under gravity thereon and a davit mounted on said second-named trackway and movable under gravity thereon, said davit being related to said second-named trackway whereby upon movement 0:! said second-named trackway on said first-named trackway, and the movement of the davit therewith, the gravitational effect upon said davlt is increased.

25. A ships davit comprising a trackway, a second trackway mounted on said first-named trackway and movable under gravity thereon and a davit mounted on said second-named trackway and movable under gravity thereon, said second-named trackway being related to said first-named trackway whereby upon movement of said second-named trackway on said first-named trackway, and the movement of the davit therewith, the gravitational effect upon said second-named trackway is decreased.

26. A ships davit comprising a trackway, a second trackway mounted on said first-named trackway and movable under gravity thereon,

and a davit mounted on said second-named trackway and movable under gravity thereon, said second-named trackway being related to said first-named trackway, and said davit being related to said second-named trackway, whereby 11131011 progressive movement of said second-named trackway on said first-named trackway, and the movement of the davit therewith, the gravitational effect upon said secondnamed trackway is progressively decreased as the gravitational efiect upon said davit is progressively increased.

27. A ships davit comprising a trackway, a second trackway mounted on said first-named trackway and. movable under gravity thereon, and a davit mounted on said second-named trackway and movable under gravity thereon, said second-named trackway being related to said first-named trackway, and said davit being related to said second-named trackway, whereby upon progressive movement of said secondnamed trackway on said first-named trackway, and the movement of the davit therewith, the

gravitational effect upon said second-named trackway is progressively decreased as the gravitational effect upon said davit is progressively increased by a leverage effect exerted by gravity upon said second-named trackway to move the davit outwardly, said leverage effect being greatest when said trackway is in its full inward position and least when in its full outward position.

28. A ship s davit comprising a trackway, a. second trackway mounted on said first-named trackway and movable under gravity thereon, and a davit mounted on said second-named trackway and movable under gravity thereon, said second-named trackway being related to said first-named trackway, and said davit being related to said second-named trackway, whereby upon progressive movement of said secondnamed trackway on said first-named trackway, and the movement of the davit therewith, the gravitational effect upon said second-named trackway is progressively decreased as the gravitational effect upon said davit is progressively increased by a leverage effect exerted by gravity upon said second-named trackway to move the davit outwardly, said leverage effect being greatest when said trackway is in its full inward position and least when in its full outward position, the outward end of the said trackway moving tangentially to the inward end whereby to effect the said gravitational leverage efiect.

THOMAS H. MARTEN. 

